Natural Polyols from Natural Products: Plant Oil Polyols

Typically, oils and fats naturally occurring in plants and animals are hydrophobic compounds that are insoluble in water. They primarily consist of glycerides of fatty acids, specifically triglycerides. Under suitable conditions, the complex mixture of triglycerides in natural oils and fats can undergo a series of chemical reactions, such as hydrolysis, transesterification, saponification, hydrogenation, oxidation, and amination, to convert them into raw materials for polyurethane production.

Plant oils are a renewable natural resource. In recent years, a few companies abroad have capitalized on the relatively low cost of plant oils, such as soybean oil and palm oil, to develop a series of plant oil-based polyols. These polyols can replace petroleum-based polyether polyols, primarily as raw materials for rigid polyurethane foam.

The United States, with its abundant soybean resources, has seen researchers develop soybean oil polyols through epoxidation and hydroxylation. These polyols have sufficiently high hydroxyl values, moderate molecular weights, and viscosities. They are used to produce rigid polyurethane foam for applications in insulation and soundproofing for buildings. The cost of these soybean oil polyols is comparable to conventional petrochemical-based polyether polyols.

Established in 1998, Urethane Soy Systems Co. (USSC) in the United States developed SoyOyl, a polyol derived from soybean oil. Its applications are nearly identical to those of petrochemical-based polyether polyols, with an annual production capacity exceeding 200,000 tons. SoyOyl has reportedly been used in producing soft foam components such as molded truck armrests, with potential applications in roofing and building rigid foam. It is said that using these polyols can reduce the cost of soft and rigid foam materials by 5%.

Malaysia, the world’s largest producer of palm oil, has researchers who modified palm oil to develop a range of palm oil polyols using cost-efficient and innovative production processes. This increases resource utilization efficiency. The natural oil polyol production process is energy-efficient, non-hazardous, and waste-free, resulting in lower costs, high efficiency, and environmental friendliness. For instance, Malaysia’s Maskimi company developed a series of palm oil polyols called "Natural Oil Polyols" (NOP). Maskimi's NOP products currently have a functionality range of 2.5 to 3.0, with higher-functionality NOPs under development. These natural oil polyols are used in rigid polyurethane foam applications, including refrigerators, construction, insulation panels, spray foam, prefabricated lightweight roofing, decorative/structural foam, large blocks, pipe insulation, and marine applications. They are also used in adhesives and elastomers. Efforts are underway to synthesize polyester polyols with sufficiently high molecular weights from palm oil for use in soft foam production.

There are also reports of combining plant and marine oils with other products to produce oligomeric polyols. These oleochemical polyols, with rigid structures and suitable hydroxyl values, are ideal for rigid polyurethane foam production. Additionally, CFCs, HCFCs, and pentane readily dissolve in these polyols.